Multi-point sash lock systems for casement windows are known. Such known systems are disclosed in U.S. Pat. Nos. 4,803,808; 5,087,087; and 5,118,145, hereby fully incorporated herein by reference. These systems typically have a single operating control, usually a lever. The lever is typically linked to a tie-bar that has multiple engaging structures disposed at intervals along its length. Operation of the lever causes the tie-bar to move longitudinally. Keepers are attached to the window sash proximate the locations of each of the engaging structures so that as the tie-bar moves, the engaging structures are moved in and out of engagement with the keepers. The entire sash lock assembly is usually concealed in the frame construction of the window, with the exception of the lever, which projects from a slot on the interior side of the window.
These known mechanisms, while being generally adequate for locking a window sash have not provided entirely satisfactory performance in some respects. Installation of the lock assembly on the window frame and sash is difficult with some prior systems because it is necessary to carefully measure and accurately position the tie-bar at the correct distance from the locked position of the window sash. If the tie-bar is located too far away from the sash location, the engaging structures will not engage the keepers. If the tie bar is too close, the engaging structures may interfere with the window sash itself. Although some prior art systems have addressed this problem by providing a locating lip on the tie-bar guide that engages in a pre-located groove in the window frame, these systems have not been entirely satisfactory in that the locating lip of the guide must fit snugly into the groove so as to avoid misalignment of the guide when it is secured to the window frame. Such misalignment may cause binding of the tie bar in the guides. Moreover, this operation consumes valuable time and effort in a mass production environment.
Further, it is necessary to locate tie bar guide structures along the length of the tie bar at optimal positions for operation of the mechanism. In some prior systems, this process must be done manually for each individual window, adding time and cost to assembly of the window. Again, although some prior systems have addressed this problem by securing the tie bar guide to the tie bar before installation with a structure that is then destroyed upon first operation of the window in order to release the guide from the tie bar, these systems have not been entirely satisfactory. In some cases, the prior systems are prone to come loose before the tie bar assembly is secured to the window frame. In addition, prior systems generally require an aperture to be formed in the tie bar that engages a structure on the guide. These systems require additional steps in manufacturing in order to form the aperture and engaging structure.
The keeper structure of prior mechanisms has not been entirely satisfactory in prior systems. Many prior systems have a keeper in which the keeper hook extends outwardly at 90 degrees from a flange portion which is secured to the window with fasteners. Such a system, which loads the fasteners axially in part, is prone to the keeper being pulled from the sash in high winds. Other systems, using a flat keeper secured to the sash are also known. These prior systems, however, generally have multiple fastener holes, which must be secured with precisely positioned fasteners, adding time and cost to window fabrication.
Also, the lever handle arrangement of some prior systems has presented particular problems during construction. It is desirable to ship the window to a construction site with the finish hardware not attached so as to prevent scratching or other damage during window shipping and installation. It is also desirable and sometimes essential, however, to operate the window prior to installation being complete. In prior systems, the window lock system cannot be operated without the finish hardware being attached.
Further, round top architectural windows having an operable sash are becoming increasingly popular. Prior art multi-point sash lock systems do not generally provide the capability of locking such a round top window sash with the same system as for the remainder of the window. The locking system should conform to the rounded side of the window and should function in a manner similar to that for a straight side.
What is needed in the industry is a multi-point sash lock system that addresses these needs.